1. Leap seconds
The 2012 leap second took Reddit down, among other sites.
Reddit is run on open source Linux operating systems, which nearly ground to a halt after the leap second was added. The problem was a subsystem in Linux. This subsystem is used when an application is sleeping and waiting for the operating system to complete another task.
In some cases it sets an alarm clock to wake the sleeping application if the OS is taking too long.
When the leap second hit, all of these subsystems were a second ahead of the main OS. This made them ring the alarm clocks, waking up countless sleeping applications at once and overloading the machines’ CPUs.
“Almost every time we have a leap second, we find something,” Linus Torvalds, Linux’s creator, told Wired. “It’s really annoying, because it’s a classic case of code that is basically never run, and thus not tested by users under their normal conditions.”
2. Connectivity problems
In July 2015 Instagram, Pinterest, Amazon and Netflix going offline for 40 minutes, and it looks like this is happening again today with Facebook, Whatsapp and Instagram.
Initially it was thought that the leap second bug had struck again, until the real reason emerged. These websites all rely on Facebook Web Services, which look like are sufferring a brief network disruption.
Facebook hosts a huge number of websites, so any issues wih them impact huge portions of the net.
Basically, they had to turn it off and on again. Luckily the problem was resolved before the hour was out, meaning Instagram users were free to continue posting gorgeously filtered photos of their food before it even had the time to go cold.
3. Hackers
Currently we’re seeing Facebook, Instagram and Whatsapp go down for about an hour, and this time the reason was disputed.
Most probably, Facebook will blame the problem on ‘a change that affected their configuration systems’.
One other possible explanation emerge 30 minutes into the outage, when a hacker group called Lizard Squad claimed responsibility for bringing the world’s favorite social media sites down.
What happens when social media sites go down?
In a word: panic.
We have grown so used to being connected via social networks that their constant supply is as important as electricity and oxygen for some people. The response tends to combine outrage, fear and humor.
When Twitter was offline briefly in January 2015, users were quick to laugh at the support team who sent a tweet about the outage, which of course would not have been visible to anyone experiencing problems.
Next time a social network goes down, we recommend staying calm, stepping away from the computer, and trying again in 30 minutes.
Social networks hate going down for any amount of time, so you can rest assured that a lot of developers are running around in a panic while being shouted at. Before too long, the service should be up and running again, and normal life will resume.